The invention relates to a transparent sheet comprising two lenticular arrays of differing pitch on opposite surfaces of the sheet, each array comprising a series of emmbossments. The invention also relates to an object comprising such a transparent sheet, a method, a single mould and a set of moulds for manufacturing said transparent sheet.
A sheet according to the opening paragraph is known from U.S. Pat. No. 3,357,773. Both surfaces of the known plastic sheet are embossed with a regular array of convex micro-lenses. The spacing between the centres of the micro-lenses in both arrays differs by a small amount. The sheet provides different Moire patterns to an observer depending on the amount by which the arrays are out of registry in one direction or in two directions in the plane of the sheet. The visual pattern stands out of the sheet and includes three-dimensional depressions or projections of circular or oval configuration and varying size.